[Bug debug/42065] DWARF .debug_macinfo contains unused macros

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065

--- Comment #5 from Eric Gallager  ---
(In reply to Eric Gallager from comment #4)
> If -feliminate-unused-debug-symbols and/or -feliminate-unused-debug-types
> start removing these, I'd want them to turn on -Wunused-macros automatically
> for me as well so I can know about it

Does the EnabledBy() thing in .opt files work across the -f/-W option prefix
boundary, or are only warnings able to enable other warnings?

[Bug debug/42065] DWARF .debug_macinfo contains unused macros

[egall at gwmail dot gwu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065

Eric Gallager  changed:

   What|Removed |Added

 CC||egall at gwmail dot gwu.edu

--- Comment #4 from Eric Gallager  ---
If -feliminate-unused-debug-symbols and/or -feliminate-unused-debug-types start
removing these, I'd want them to turn on -Wunused-macros automatically for me
as well so I can know about it

[Bug debug/42065] DWARF .debug_macinfo contains unused macros

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065

Martin Sebor  changed:

   What|Removed |Added

   Keywords||missed-optimization
 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-02-07
 CC||msebor at gcc dot gnu.org
 Ever confirmed|0   |1

--- Comment #3 from Martin Sebor  ---
It doesn't look like this has changed between GCC 4.5 and GCC 7 so I'll confirm
it as a missing space optimization.

$ cat t.c && gcc -g3 -Wall -feliminate-unused-debug-symbols
-feliminate-unused-debug-types t.c && readelf -wm a.out | grep -e NOT -e USED
#define NOT used
#define USED(x) x
int main (void) { return USED (0); }
 DW_MACRO_GNU_define_indirect - lineno : 1 macro : NOT used
 DW_MACRO_GNU_define_indirect - lineno : 2 macro : USED(x) x

With GCC 7, even an empty object file contains 345 macro definitions (one for
each macro predefined by GCC):

$ /build/gcc-trunk/gcc/xgcc -B /build/gcc-trunk/gcc -c -g3 -xc -ot.o -

[Bug debug/42065] DWARF .debug_macinfo contains unused macros

[pinskia at gmail dot com]

--- Comment #1 from pinskia at gmail dot com  2009-11-16 14:31 ---
Subject: Re:   New: DWARF .debug_macinfo contains unused macros



Sent from my iPhone

On Nov 16, 2009, at 6:12 AM, jan dot kratochvil at redhat dot com
gcc-bugzi...@gcc.gnu.org 
  wrote:

 -g3 currently produces huge objects as it contains many unused macros.
 -g2 produces no macros debug info so GDB cannot provide its expansion.


That is by design and the reason why -g is -g2 by default 



 There is no way to store just the used macros.

 (debuginfo compression driven by Roland McGrath may eliminate them but
 still...)

 While even a macro never used by a program can be helpful in most  
 cases IMO it
 is enough to provide the macro definitions touched by the code being  
 debugged.

 -feliminate-unused-debug-symbols -feliminate-unused-debug-types have  
 no effect.

 --- 
 --- 
 --- 
 --
 #define NOT used
 #define USED(x) x
 int main (void) { return USED (0); }
 --- 
 --- 
 --- 
 --

 Getting:
 gcc -g3 -o unusedmacro unusedmacro.c -Wall; readelf -wm unusedmacro
 DW_MACINFO_define - lineno : 1 macro : NOT used
 DW_MACINFO_define - lineno : 2 macro : USED(x) x

 or:
 gcc -g2 -o unusedmacro unusedmacro.c -Wall; readelf -wm unusedmacro
 nothing printed

 Expected output:
 gcc -g3 -o unusedmacro unusedmacro.c -Wall; readelf -wm unusedmacro
 DW_MACINFO_define - lineno : 2 macro : USED(x) x


 -- 
   Summary: DWARF .debug_macinfo contains unused macros
   Product: gcc
   Version: 4.5.0
Status: UNCONFIRMED
  Severity: minor
  Priority: P3
 Component: debug
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jan dot kratochvil at redhat dot com
 GCC target triplet: x86_64-unknown-linux-gnu


 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065

[Bug debug/42065] DWARF .debug_macinfo contains unused macros

[jan dot kratochvil at redhat dot com]

--- Comment #2 from jan dot kratochvil at redhat dot com  2009-11-16 14:49 
---
(In reply to comment #1)
  -g3 currently produces huge objects as it contains many unused macros.
  -g2 produces no macros debug info so GDB cannot provide its expansion.
 
 That is by design and the reason why -g is -g2 by default 

OK, thanks for info, still IMO there should be such an additional option.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42065